Abstract: Inappropriate expression of genes such as the homeotic (HOX) genes is found in up to 40% of cases of Acute Myelogenous Leukemia (AML). Two well-known genetic subsets, those with MLL-rearrangements and those with NPM1 mutations, are known to possess high-level expression of HOX genes and have been shown to be dependent on continued expression of these genes. Recent studies have defined the protein complexes that maintain this aberrant gene expression. Furthermore, multiple groups and pharma/biotech companies have now developed small molecule inhibitors of these complexes. Some of these small molecules, particularly those targeting DOT1L, EZH2 and Bromodomains) have recently entered early phase trials and have shown interesting biological and some complete clinical responses. Another approach to target chromatin associated complexes is inhibition of the MLL1-Menin interaction, an approach that has also been shown to reverse HOX gene expression. In this proposal we will characterize newly developed MLL1-Menin inhibitors and work to bring one of these small molecules to clinical assessment. In Specific Aim 1 we will characterize the effects on gene expression and chromatin state after inhibition of the MLL1-Menin interaction in MLL-rearranged and NPM1 mutant AML cells. In Specific Aim 2 we will assess the combination of MLL1-Menin inhibitors with either azacitidine, DOT1L inhibitors or FLT3 inhibitors. In Specific Aim 3 we will initiate a phase 1 trial of MLL-1 Menin inhibitors alone and in combination with a azacitidine. These trials that will set the foundation for further assessment of combinations based on results from preclinical studies described here. The proposed experiments will propel MLL1-Menin inhibitors to clinical assessment and importantly define combination approaches that should be assessed in future clinical studies.